Reversing mechanism for machine tools



Aug. 27, 1935. w. F. FRASER REVERSING MEcHANI-SM 'FOR MACHINE TOOLS 3Sheets-Sheet 1 Filed Aug. 27. 1928 @nl HIIII .TIIIIIllII A gwueoz MRRENl1". FRASER a. @HWQW' WITNEssEs M yH. gm, mana-@bl-am I Aug. 27, 1935.w. F. FRASER 2,012,273

' REVERSING MEcHANIsMFoR MACHINE ToLs Filed Aug. 2v. 1928 s sheets-sheet2 gwen/woz WITNEssEs MRRE-N E FRASER,

V www Aug. 27, 1935. w.-F. FRASERA 2,012,273

REVERSING MEGHANISM FR MACHINE TOOLS Filed Aug. 27. 1928 3 Sheets-Sheet5 y Patented Aug. 27, 1-935 UNITED STATES REVERSING MECHANISM FORMACHINE TOOLS Warren F. Fraser, Westboro, Mass., assgnor to NortonCompany, Worcester, Mass., a corporation of Massachusetts ApplicationAugust 27, 1928, Serial No. 302,407

15 Claims.

'Ihis invention relates to machine tools and more particularly to areversing mechanism operated by fluid under pressure.

Heretofore various reversing mechanisms have been devised forcontrolling the reciprocating movement of machine tool tables and thelike by iiuid under pressure in which a piston and cylinder mechanismwere utilized to transmit movement to the table. lThese mechanisms havebeen fairly satisfactory on tables which are reciprocated at a moderatespeed. In modern production grinding and other machine tool operations,it is essential'to get the maximum production per machine. This demandhas been partly met by increasing the lspeed of machine tool tables andalso other parts of the machine to get `the maximum production out of aAgiven machine. It has been found that the ordinary iiuid operatedreversing mechanism as well as most mechanical mechanisms are notsatisfactory where a rapidly moving table is employed due to undueshocks and vibrations incident to the revcrsal in direction of a rapidlymoving table.

The previous'mechanisms have relied upon a shocks and vibrations to betransmitted to the 35 cable as it is reversed. This detrimentauy assetsthe machine operation being performed in thatA the shocks and vibrationsare transmitted to produce chatter marks on the surface of the work.

-It is one object of this invention to provide a fluid controlledapparatus to reciprocate the table at a rapid speed so that the tablemay be reversed in direction with an easy stopping and starting actionwhereby shocks and vibrations are reduced to a It is another object ofthis invention to provide a suitable valve mechanism'so that the speedof the table may be gradually retarded prior to reversal to cause aneasy stopping of the. table.

A It is still another object ci this invention to f provide an automaticfluid pressure operated mechanism for reversing the movement of thetable at the end of its stroke so arranged as to gradually retard themovement of the table prior to reversal and to thereafter accelerate themovement of the table to its normal speed.

It' is a further object; to4 provide. a manually operable mechanism sothat the operator may at any time during the table travel reverse thedirection of movement of the table without undue shocks and vibrationand cause the table to reverse atrapproximately a predeterminedposition.

It is still a further object of this invention to provide suitableadjustments for the throttle valve mechanism so that the normal speed ofthe table may be adjusted and also so arranged as to adjust the extentof the throttling action during the reversing period.

As illustrated in the drawings, a mechanism '15 has been showndisclosing one embodiment of the invention. It should be understood thatapplicant does not wish to be limited to this particular embodiment ofhis invention but that this invention covers broadly any mechanismembodying the subject matter of the claims appended hereto. In thedrawings in which like reference numerals indicate like parts:

Fig. 1 is a fragmentary front elevation of a machine tool embodying thisinvention, having parts broken away and shown in section to more clearlyillustrate the construction;

Fig. 2 is a sectional viewthrough the valve mechanism takenapproximately on the line 2-2 of Fig. 1; I

Fig. 3 is an enlarged fragmentary sectional view taken through the baseof the machineapproximately on the line 3-3 vof Fig. 1 showing the valveand control mechanism in elevation;

Fig. 4 is a diagrammatic view of the hydraulic system, showing thevalves in position as the table starts its movement towards the left, asviewed in Figs. 1 and 4.

This invention consists broadly in a iiuid op- 40` l erated mechanismarranged to reciprocate a machine table at a rapid speed but arranged sothat the reversal in direction of travel may be obtained without shocksand vibrations. A valve kmechanism is provided `which is automaticallyoperated to control the admissionof fluid to each end of said mechanismto cause a reversal in the direction of travel of the table at thedesired point. Cooperating with the reversing valve is a throttlingdevice arranged to throttle the fiuidentering and leaving the system tocause an easy starting and stopping action at reversal. This mechanismcomprises a throttle valve arranged to regulate the normal speed of thetable and also arranged so that it may be gradually closed prior toreversal and gradually opened after reversal to retard and acceleratethe movement of the table during 4the period of reversal to effect aneasy stopping and starting action.

5 The throttle valve is so arranged as to throttle table Il adapted toslide on the usual V-way I2 Y and flat-way I3. To reciprocate the tableII a mechanismoperated by iluidunder pressure such as a chamber having amember movably mounted therein for'actuation by said pressure may beutilized. As illustrated in the drawings, a cylinder chamber I5 issupported by brackets I6 bolted to the inner portion of the base I0. Apiston I'l is slidably mounted within the cylinder I5 and is providedwith a piston rod I8 connected at its outer end to a bracket I9depending from the table Il. It will thus be seen that any movement ofthe piston within the cylinder is transmitted to produce correspondingmovement oi the table III.

To control the movement of the piston within the cylinder, a valvemechanism may be utilized which is arranged to produce a gradualretardation and acceleration of the -moving part when reversed indirection of travel. As shown in the drawings, a valve mechanism 20 isbolted to the front of the machine base. The valve mechanism 20comprises two valves, namely, a reversing valve 22 arranged to controlthe direction oi' ow of iiuid to and from the cylinder I5 and a throttlevalve 21,. interposed between the reversing valve and the source ofsupply, to control the speed of the table and also arranged to permit a.

gradual retardation and acceleration of the y movement of the tableprior to and after reversal to minimize shocks and vibrations. Thismechanism comprises a reverse valve 22 which is slidably mountedwithinvthe sleeve 23. 'Ihe valve slide within the sleeve 3l tosimultaneously throttle both the intake and exhaust of iluid to thereverse valve, thereby permitting a more uniform control of the tablespeed.

Any suitable source of fluid under pressure may be utilized to supplyIand operate the system, such as a pump 32`in the base to force iiuidfroma.

reservoir 33 in the base to the throttle valve, reversing valve and tothe cylinder. This part of the mechanism has been illustrated onlydiagrammatically'since it is old and well known in the art, and is notconsidered part of applicants invention. Fluid entering the systempasses through a conduit 34 and. a port 35 int'o a chamberY 36 betweenthe pistons 28 and 28AA of the throttle valve 21. The inlet port 35 may'comprise a single opening or a plurality of openings arranged about thesleeve as shown in the drawings. The fluid under pressure passes throughthe chamber 36 and is forced upwardly through a port 31 in the sleeve 3|into a passage 38 as shown in dotted lines in Fig. 1. This passageconveys iiuid through a port 4I) in the sleeve 23 into a chamber 4Ibetween the pistons 24 and 25 (as shown in Fig. l) Fluid passes throughthis chamber and is forced outwardly through the port 42 in sleeve 23,the conduit 43 and the port 44 into the left-hand end of cylinder I5 asviewed in Fig. l. The iluid entering and passing through the valves inthis direction forces the piston I1 toward the right as viewed in Fig. 1and transmits a corresponding movement tothe table Il through thepreviously described connections.

In order that the table may be reversed automatically at the end of thedesired stroke, a mechanism is provided to operate the reversing valveat the desired time to change it to its opposite position and therebyreverse the flow of uid to the cylinder I5. As shown in the drawings, Iprovide a reversing lever 48 which is' mounted on a stud 49 on the frontof the base I8. A link 50 is pivotally connected to the lever 48 by astud 5i.y The other end of the link 50 is provided with a pin 52 whichis slidably mounted in an elongated slot 53 in the member 54 on the endof the valve 22. The elongated slot is provided to permit a movement ofthe reversing lever 48 without transmitting movement to the reversingvalve.

A load and re mechanism is provided to hold the lever 48 in the desiredposition to control the reversing valve 22. As shown in the drawings, alever 55 is pivotally mounted on a stud 5G and has at its other end aV-shaped projection 51 adapted to contact with a similarly shapedprojection 58 on the rear side of the lever 48. The lever 55 ispreferably under tension so that the projection 51 is held in contactwith the projection 58. As shown in the drawings, one end of a spring 59is connected to a pin 60 on the lever 55.and its other end is connectedto a pin 6l on the iront of the machine base. this construction that asthe operator moves the lever 48 toward the right, as viewed in Fig. l,the projection 58 will coact with the V-shaped end 51 to raise the lever55 and thereby increase the tensionon the spring 59. 'I'his movementcontinues until the high point on the projection 58 passes the highpoint on the projection 51 at which time-the released tension of thespring rapidly moves the valve 22 into' the reverse position. Theelongated slot 53 is provided so that the lever 48 is permitted to moveuntil the high point on the projection 58 passes the high point on theprojection 51 without transmitting any movement to the reversingvalve22.

A stop pin 62 is provided in the cylinder head 63 of the reversing valve22 to vlirnit the movement of the valve toward the right so as toproperly position the pistons thereon relative to the ports in thesleeve 23. A collar 64 is provided on the valve stem 22 so positioned asto limit the movement of the4 valve toward the left to similarlyposition the valve relative to the corresponding ports in the sleeve.

In order that the lever 48 may be shifted automatically at the desiredpoint, a pair of adjustable dogsl65 and'GG are provided which aresupported by the bolts 61V andy 68 having their heads69slidablymountedinthe T-slot 10 formed in the front edge of the machinetable. 'Ihe dogs S5 and 86 are provided with pins 12 and 13 respectivelywhich are adapted-to contact with the adjustable screws 14 and 15 on thereversin lever 48.

It will be readily apparent from Assuming the table to be traveling inthe direction of the arrow 4(Fig. 1), this movement con-v on theV-shaped end 51 at which point the released tension-of the spring 59acts to rapidly throw the reversing valve 22 toward 'the right andthereby change the direction of flow of fluid to and from the cylinderI5.

While the fluid is owing through the conduit 43 through the port 44 intothe left-hand end of the cylinder I5, it is exhausting from the-` otherend of the cylinder through a port 18 and a'conduit 19 through a port 80in sleeve 23 into a chamber 8| between the piston 25 and the cylinderhead 63. The fluid then passes through an exhaust port 82 in sleeve 23and a passage 83 to the throttle valve 21. The exhaust fluid enters thethrottle valve through a port 84 in sleeve 3| into a chamber 85 betweenpistons 29 and 30 and passes out of this chamber through a port 86 insleeve 3| and conduit 81 into the reservoir 33.

When the reversing valve 22 moves toward the right into a reverseposition, the fluid passes through the throttle valve 21 in the samedirection and then through port 40 into the chamber 4| between thepistons 24 and 25 and out through a port 80 in sleeve v23 and theconduit 19 and through the port 18 into the right-hand end of cylinderI5, as viewed in Fig. 1. 'Ihis movement forces the piston I1 towardv theleft and transmits a corresponding movement to the table II. In thisposition of the reversing valve, fluid is exhausted from the left-handend of the cylinder I5 through port 44, conduit 43, port 42 in thesleeve 23 into a chamber 88 between the piston 24 and a cylinder head89. The fluid is then forced through a port 90 into the passage 83 andport 84 in the sleeve 3| into the chamber 85 between the pistons 29 and30 and then exhausts through port 86 and conduit 81 to thereservoir 33.

As shown in Fig. 1, the throttle valve is wide open so as to permit amaximum flow offluid through the intake and exhaust ports to obtain amaximum speed on the work table. By adjust- 'i ing the position of thethrottle valve`21, that is, by moving it toward the right, both theintake and exhaust ports may be throttled to give the desired speed tothe reciprocable table.

To obtain an easy stopping and starting of the table during the periodof reversal, a mechanism is provided to gradually close and open thethrottle valve so as to retard and accelerate the movement of the tablebefore and after the reversing valve is shifted into its reverseposition. As shown in the drawings, a bell crank lever l9| is pivoted ona stud 92on the front of the machine base. One arm of the bell crankisprovided witha follower roller 93, the other ,end is provided 'with anadjustable screw 94 arranged to contact with the end of the throttlevalve 21 so that any movement of ,the lever 9| is transmitted to give acorresponding movement of the throttle valve. i

In order that the throttle valve may be moved automatically in timedrelation with the movement of the reversing valve, a pair of cam platesand 96are provided and mounted on the dogs 65 and 66 respectively. Asthe table moves toward the right, as viewed inFig. 1, the cam 95contacts with the follower roller 93 on the bell crank lever 9| beforethe pin 12 contacts withl the screw 14. As the table continues itsmovement toward the right, the cam 95 forces the roller 93 downwardly,thereby rocks lever 9| and transmits motion to the adjustable screw 94and moves the throttle valve 21 toward the right to gradually close thethrottle valve. The throt- -tling -movement may be controlled as desiredby varying the shape of the cams 95 and 96. It will be readily seen fromthis construction, that the throttle valve is closed gradually' to checkthe ow of uid passing through the hydraulic system and to slow down themovement of the table before the load and re mechanism operates to shiftthe reversing valve 22 into a reverse position. After the reversingvalve has shifted, the fluidl starts flowing in the opposite directionthrough the reversing valve and cylin'der and operates to move the tableI I in the opposite direction. As this movement continues, `the roller93 rides up theface of the cam 95 and gradually opens the throttle valvethereby increasing the flow of fluid through the hydraulic system andaccelerating the movement of the table to its normal speed.

The table continues to move toward the left, as viewed in Fig. 1, untilthe follower roller 93 contacts with the cam 96 which acts to give a4similar throttling action before and after the reversing valve 22 isshifted into a reverse position. This cycle of operation is continued ateach reversal of the table. l e

A stop mechanism is preferably provided to vided with a spring pressedplunger |0I, the details of which have not been shown since these areold and well known in the art. This plunger |0| is adapted to engagenotches |02 in the arcuate member |03. It will be readily apparent fromthis construction, that by moving the lever |00 toward the right, thecam 98 will turn and move the throttling valve. This adjustment isprovided so that the throttling valve may be positioned to give thedesired normal speed to the table I.

A spring |04 is provided at the end of the valve 21 -so as to maintainthe valve stem in contact with the adjustable screw 94 and also tomaintain the head ofthe screw 94 in operative engagement with the4 cam98. The cam 98 is adjusted to the desired position to give the properspeed to the table and is thenleft in adjusted position.

It may be desirable to vary the amount of throttling movement of thevalve 21 during the reversal period. The adjustable screw 94 is providedfor this purpose. By turning this screw, the ends of which are fixedrelative to the cam 98, the position of the bell `crank lever 9| changesto vary the point at which the roller 93 contacts with the cams 95 and96 relative to the pins 12 and 13 striking the screws 14 and 15 on thereversing lever 48. By this adjustment the operator may determine theamount of the gradual slowing down of the table prior to the throwing ofthe removement of the table manually so that at any time du'ring thenormal stroke of the table, it may be reversed without waiting-for thedogs to operate and automatically reverse the table. To this end, asuitable manual control is provided. supplementing the mechanismheretofore described so that the throttle valve 21 may be closedgradually When the operator swings the reversing lever 48 by hand. Thelever 55 is preferably formed asa bell crank lever having a short arm'|05 provided with an adjustable screw |06 adapted to. contact with alever |01 which is integral with the bell crank lever 9|. As theoperator grasps the reversing lever 48 and moves it toward the right, asviewed in Fig. 1, the projection 58 on the lever coacting with theV-shaped end 51 of the lever 55 rocks the lever about its stud 56. Thismovement acting through the lever |05 and screw |06 swings the lever |01and bell crank 9| to slide the throttle valve 21 toward the right andthereby throttle the fluid passing through the valve. By this mechanism,the operator may reverse the .table at any time during its strokewithout causing undue shocks and vibration inasmuch as the throttlevalve 21 is actuated by the manual movement of the reverslng lever 48 toslow down the movement of the table l! before the reversing valve isshifted.

ln the operation of my device, the operator opens the valve controllingthe fluid pressure line or starts the pump in motion which admits fluidthrough the throttle valve 21 and the reversing valve 22 to reciprocatethe tablell. erator then moves the lever |00 to adjust the position ofthe throttle valve 21 to give the desired table speed for the operationto be performed. After this adjustment is made, the operator may thenadjustthe position of the screw 94 relative to the bell crank lever 9|to vary the amount of throttling movement at reversal to give thedesired retarding and accelerating action just prior to and after thereversing valve 22 is shifted.

After these adjustments are made, the `dogs 65 and 66 may be adjustedrelative to the table to give the desired length of stroke and toposition the table relative to the Work. The screws 14 and 15 may beadjusted relative to the lever 48 to vary the time between which the camg5 strikes the roller 93 and thel pin 12 striking the screw 14. By thisadjustment, the operator may vary the amount of movement of the tablebetween the beginning of the throttle action and the shifting of thereverse valve.

Having thus described the invention, what is claimed as new and desiredto secure by Letters Patent is:

l. A reversing mechanisml for a machine tool table comprising a lluidpressure actuated'motor connected to move the table, a source of uidpressure, means including a reversing valve for admitting and exhaustingfluid under pressure to said motor, a throttle valve controlling theexhaust of fluid from the motor, means to adjust the position of saidthrottle valve to control the normal table speed, and means controlledby the table movement for gradually closing said throttle valve to causean easy reversal of the table.

2. A reversing mechanism for machine' tool tables comprising a fluidchamber, a member movably mounted within said chamber and op erativelyconnected to reciprocate the table, a reversing mechanism including avalve operatively connected to admit iluid under pressure to either endof said chamber and a throttle valve arranged to simultaneously throttlethe intake and exhaust of fluid to and from the reversing valve.

The op- 3. A reversing mechanism for machine tool tables comprising acylinder and piston connected to reciprocate said table and a reversingmechanism including a. valve operatively connected to admit fluid underpressure to either end of said cylinder and a throttle valve arranged tosimultaneously throttle the inflow and exhaust of fluid to and from thereversing valve.

4. A reciprocating mechanism for machine tool tables comprising acylinder and piston arranged to reciprocate said table, a reversingmechanism including a. valve operatively connected to admit iluid underpressure to eitherend of said cylinder, a throttle valve controlling theexhaust of uid from the cylinder, means to adjust the throttle valve tocontrol the ow of fluid and thereby produce the desired table speed, andmeans actuated by the table movement to gradually close said throttlevalve to retard the Y movement of the table at reversal.

5. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to reciprocate said table, a pump to force uid underpressure to said cylinder, a fluid reservoir, a reversing mechanismincluding a valve opel" atively connected to admit fluid under pressureto either Vend of said cylinder, a throttle valve arranged tosimultaneously throttle the inflow and exhaust of iluid, and means togradually close said throttle valve to retard the movement of thetable'at reversal.

6. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to reciprocate said table, a source of iluid underpressure, a reversing mechanism including a reversing valveoperativelyconnected to admit iiuid under pressure to either end of saidcylln der, a throttle valve arranged to simultaneously throttle theinflow and exhaust of uid, means to adjust the position of said throttlevalve to give the desired table speed, and means to gradually close andopen said throttle valve to gradually retard and accelerate the movementof the table at reversal.

7. A reversing mechanism for machine tool tables comprising a cylinderand piston'arranged to reciprocate said table, a source of fluid underpressure, a reversing mechanism including a valve actuated by said tableto change the direction of flow of fluid under pressure to saidcylinder, a 'throttle valve arranged to control the exhaust of luid fromthe reversing valve, means actuated by movement of said table togradually open said throttle valve at reversal at each end of the tablestroke to cause an easy starting of the table and means to adjust theextent of movement of the throttle valve to regulate the reversal-of thetable at' each end of its stroke.

Y 8. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to reciprocate said table, a pump to force :duidunder pressure to said cylinder, a fluid reservoir, a reversingmechanism including a valve to change the direction of ow of fluid underpressure to said cylinder, a lever to actuate said valve. adjustabledogs on said table to actuate said lever, a throttle valve arranged tocontrol the cw of fluid through the reversing valve, means l to adjustthe position of said throttle valve lto tables comprising a cylinder andpiston arranged to reciprocate sai-d table, a pump to force fluid underpressure to said cylinder, a fluid reservoir, a reversing mechanismincluding a valve to change the direction of ovv of fluid under pressureto said cylinder, a throttle valve arranged to control the flow of fluidthrough the reversing valve and cylinder, and a manually operable leverconnected to actuate said reversing valve, and means actuated by saidlever to gradually close and open the throttle valve prior to and afterthe operation of the reversing valve.

l1. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to' reciprocate said table, a source of fluid underpressure, a reversing mechanism including a Vvalve operatively connectedto admit fluid under pressure to either end of said cylinder, a throttlevalve arranged to control the flow of uid through the reversing valve,manual means to adjust the position of said throttle valve to controlthe normal speed of the table, and a manually operable lever connectedand arranged to gradually close the throttle valve to retard the speedof the table prior to reversal and to actuate said reverse valve.

12. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to reciprocate s-aid table, a source of fluidpressure, a reversing mechanism including a valve operatively connectedto admit fluid to either end of the cylinder, a 4throttle valve tocontrol the flow of fluid through the reversing valve, means to adjustthe position of said throttle valve to regulate the normal speed of thetable, and means operable by movement of said table to gradually closethe throttle valve prior to reversal to slow down the movement of thetable, and

manually adjustable means to vary the extent of movement of saidthrottle valve.

13. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to reciprocate said table, a pump to force fluidunder pressure to saidcylinder, a uid reservoir, a reversing mechanismincluding a valve arranged tocontrol the ow of fluid under pressure toeither end of said cylinder, a throttle valve to control the flow offluid through said reverse valve, adjust-able means to position saidthrottle valve to control the normal speed of said. table, a lever toactuate saidreverse valve, dogs on the table to actuate said lever, asecond lever arranged to actuate s-aid throttle valve, cams on saidtable arranged to gradually close and open said throttle vvalve prior toand after reversal to retard and accelerate the table at reversal, andmeans to adjust the amount of throttling movement of said valve .todetermine the speed of the table at the point of reversal.

14. A reversing mechanism for machine tool tables comprising a cylinderand piston arranged to reciprocate said table, means inclu-ding a pumpto force fluid under pressure to said cylinder, a reversing mechanismincluding a valve to change the direction of oW of fluid under pressureto said cylinder, a throttle valve arranged to control the flow of fluidthrough the reversing valve, means including a cam to adjust theposition of sai-d throttle valve to control the normal 'table speed,means actuated by movement of the table to gradually close the throttlevalve and slow down the table and to thereafter actuate said reversevalve to change the direction of travel of the table, and manuallyadjustable means to vary the extent of movement of said throttle valve.

15. A reversing mechanism for machine tool tables comprising a uidchamber, a member movably mounted Within said chamber and operativelyconnected to reciprocate the table, a reversing mechanism including avalve operatively connected to admit fluid under pressure to either endof said chamber, a throttle valve arranged to simultaneously throttlethe intake and exhaust of fluid to and from the reversing valve, meansto gradually close and open said throttle valvel to graduall" retard andaccelerate the movement of the table at reversal, and means to adjustthe extent of movement of the throttle valve to regulate the reversal ofthe table.

WARREN F. FRASER'.

